Pharmacokinetic evidence for the induction of lopinavir metabolism by efavirenz

Abstract

Aims: The influence of efavirenz on lopinavir pharmacokinetics was investigated using a population approach. Methods: Forty-five HIV patients treated with lopinavir/ritonavir plus efavirenz (A) and 24 patients treated with lopinavir/ritonavir plus nucleoside/nucleotide reverse transcriptase inhibitors (B) were studied. Results: A relationship (P < 0.01) was established between the elimination rate constant of lopinavir (k10) and treatment with efavirenz. Mean k10 was higher in group A than in group B (0.3838 vs 0.2810 h-1) (P < 0.001, 95% confidence interval for difference between means 0.1004, 0.1052). Conclusions: These results suggest that lopinavir metabolism is induced by efavirenz. © 2005 Blackwell Publishing Ltd.